Re: [PATCH v4 03/11] drm/bridge: cdns-dsi: Fix Phy _init() and _exit()

[Aradhya Bhatia <a-bhatia1@ti.com>]

Hi Tomi,

Thanks for reviewing the patches!

On 26/06/24 15:55, Tomi Valkeinen wrote:
> Hi,
> 
> On 22/06/2024 14:09, Aradhya Bhatia wrote:
>> Initialize the Phy during the cdns-dsi _resume(), and de-initialize it
>> during the _suspend().
>>
>> Also power-off the Phy from bridge_disable.
>>
>> Fixes: fced5a364dee ("drm/bridge: cdns: Convert to phy framework")
>> Signed-off-by: Aradhya Bhatia <a-bhatia1@ti.com>
>> ---
>>   drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c | 10 ++++++++--
>>   1 file changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
>> b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
>> index 5159c3f0853e..d89c32bae2b9 100644
>> --- a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
>> +++ b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
>> @@ -672,6 +672,10 @@ static void cdns_dsi_bridge_disable(struct
>> drm_bridge *bridge)
>>       if (dsi->platform_ops && dsi->platform_ops->disable)
>>           dsi->platform_ops->disable(dsi);
>>   +    phy_power_off(dsi->dphy);
>> +    dsi->link_initialized = false;
>> +    dsi->phy_initialized = false;
>> +
>>       pm_runtime_put(dsi->base.dev);
>>   }
>>   @@ -698,7 +702,6 @@ static void cdns_dsi_hs_init(struct cdns_dsi *dsi)
>>              DPHY_CMN_PDN | DPHY_PLL_PDN,
>>              dsi->regs + MCTL_DPHY_CFG0);
>>   -    phy_init(dsi->dphy);
>>       phy_set_mode(dsi->dphy, PHY_MODE_MIPI_DPHY);
>>       phy_configure(dsi->dphy, &output->phy_opts);
>>       phy_power_on(dsi->dphy);
>> @@ -1120,6 +1123,8 @@ static int __maybe_unused cdns_dsi_resume(struct
>> device *dev)
>>       clk_prepare_enable(dsi->dsi_p_clk);
>>       clk_prepare_enable(dsi->dsi_sys_clk);
>>   +    phy_init(dsi->dphy);
>> +
>>       return 0;
>>   }
>>   @@ -1127,10 +1132,11 @@ static int __maybe_unused
>> cdns_dsi_suspend(struct device *dev)
>>   {
>>       struct cdns_dsi *dsi = dev_get_drvdata(dev);
>>   +    phy_exit(dsi->dphy);
>> +
>>       clk_disable_unprepare(dsi->dsi_sys_clk);
>>       clk_disable_unprepare(dsi->dsi_p_clk);
>>       reset_control_assert(dsi->dsi_p_rst);
>> -    dsi->link_initialized = false;
>>       return 0;
>>   }
>>   
> 
> So with this patch, phy_init/exit will be called in the resume/suspend
> functions. That looks fine.
> 
> But the phy_power_on/phy_power_off looks odd to me. Here you add
> phy_power_off() to cdns_dsi_bridge_disable(), which sounds fine. But
> phy_power_on() is called in cdns_dsi_hs_init(), and that is called in
> cdns_dsi_bridge_enable() (which sounds fine), but also in
> cdns_dsi_bridge_pre_enable().
> 
> So doesn't that mean cdns_dsi_hs_init() call in cdns_dsi_bridge_enable()
> is extra, as it effectively does nothing (it exists right away if
> dsi->phy_initialized == true)?

That's right. When cdns_dsi_hs_init() is called from
cdns_dsi_bridge_enable(), it is simply expected to return since
phy_initialized is true.

I am not aware about the exact reasoning behind this, but this gets
addressed when I convert the _bridge_enable() to _bridge_pre_enable()
and drop the older _bridge_pre_enable() entirely.


Regards
Aradhya